The fall webworm is not considered an important forest pest. However,
ugly webs can seriously detract from aesthetic values. The preferred
hosts in the South are persimmon, pecan, and sourwood, but it is also
found on black walnut, hickory, cherry, sycamore, crab apple, and
sweetgum. The insects range throughout North America.
[Illustration: Fall webworm larva.]
The adult is a pure white moth about 1¼ inches long. The forewing is
sometimes marked with blackish dots. The larva is about one inch long
when full grown, generally pale yellow or greenish with a broad dark
longitudinal stripe on the back and a yellowish stripe extending from
black and orange warts. The insect has one generation per year in the
northern part of its range, and two in the southern part. Moths of the
first generation emerge from May to July and those of the second in July
and August. Adult females lay 400-500 eggs in white cottony patches on
the underside of the leaves of host plants. The eggs hatch in about a
week, and the larvae form a web and begin to skeletonize the leaves by
feeding in rows. As the larvae grow they expand the web to cover the
colony. When the larvae are ready to pupate, they crawl or drop to the
ground and form a brownish cocoon in the duff around the tree where they
overwinter.
[Illustration: Fall webworm infestation.]
Natural enemies usually keep this insect under control. Webs can be
pruned from high-value trees in scenic or recreation areas.